A Practical Guide to Haemostasis

Estimating the Risk of Venous Thromboembolic Disease [VTED] in Pregnancy


Venous Thromboembolic Disease [VTED] leading to a Pulmonary Embolism is a leading cause of maternal death in the UK and venous thromboembolism complicates ~1.2 in every 1000 deliveries.  A significant number of fatal antenatal VTE events occur in the first trimester of pregnancy and therefore, all women should undergo a VTE risk assessment in early pregnancy or pre-pregnancy. This should be repeated if a woman is admitted to hospital for any reason and again intrapartum or post-partum . The absolute risk of VTED in pregnancy is low and therefore, a risk assessment algorithm allows the identification of at-risk women and who may benefit from thromboprophylaxis with a Low Molecular Weight Heparin [LMWH].

The Royal College of Obstetricians & Gynaecologists:
Estimating the Risk of VTED in Pregnancy

The Royal College of Obstetricians & Gynaecologists have published guidelines on the assessment of women for VTED in pregnancy and pre-pregnancy and the management of women who have developed a venous thrombosis/pulmonary embolism in pregnancy - see References for additional information.
The RCOG risk assessment algorithm is summarised below. A number of other risk assessment protocols have been developed - see References.

Select Criteria:

Pre-existing Risk Factors
Previous VTE [except a single event related to surgery]
4 Points
Previous VTE provoked by major surgery
3 Points
Known High-risk Thrombophilia1
3 Points
Medical co-morbidities2
3 Points
Family History of unprovoked or oestrogen-related VTE in first-degree relative
1 Point
Known Low-risk Thrombophilia [No VTE]3
1 Point
Age >35 yrs
1 Point
  BMI >30 Kg/M2   1 Point
  BMI >40 Kg/M2  2 Points
Parity ≥3
1 Point
1 Point
Gross Varicose Veins
1 Point
Obstetric Risk Factors
Pre-eclampsia in current pregnancy
1 Point
ART or IVF [Antenatal only]
[Assisted Reproductive Technology; In-vitro Fertilisation]
1 Point
Multiple pregnancy
1 Point
Caesarean section in Labour
2 Points
Elective Caesarean section
1 Point
Mid-cavity or rotational operative delivery
1 Point
Prolonged labour <24 hours]
1 Point
Post-Partum Haemorrhage [PPH] > 1 litre or Transfusion
1 Point
Pre-term birth [<37 weeks] in current pregnancy
1 Point
Stillbirth in current pregnancy
1 Point
Transient Risk Factors
Surgical procedure in pregnancy or puerperium
[Except immediate repair of the perineum]
3 Points
Hyperemesis, Dehydration
3 Points
OHSS [First trimester only]
[Ovarian HyperStimulation Syndrome]
4 Points
Current systemic infection [requiring iv antibiotics of hospital admission
1 Point
1 Point

1. High Risk Thrombophilia: This includes Antithrombin deficiency, Protein S deficiency, Protein C deficiency, combined Factor V Leiden mutation and the Prothrombin G20210A mutation.
Persistent Antiphospholipid antibodies [Lupus anticoagulant and/or Anticardiolipin antibodies or Anti-β2Glycoprotein I [anti-β2GPI] antibodies. - should be considered as risk factors for thrombosis in pregnancy.
2. Medical co-morbidities include: cancer, heart failure; active SLE, inflammatory polyarthropathy or inflammatory bowel disease; nephrotic syndrome; Type 1 diabetes mellitus with nephropathy; sickle cell disease; current intravenous drug user.
3. If there is a known low-risk thrombophilia in a woman with a family history of VTE in a first-degree relative, postpartum thromboprophylaxis should be continued for 6 weeks. Low risk Thrombophilia includes heterozygosity for the Factor V Leiden mutation and heterozygosity for the Prothrombin G20210A mutation.

Total Score

≥4 Antenatally Consider Thromboprophylaxis from the first trimester
3 Antenatally Consider Thromboprophylaxis from 28 weeks
≥2 Postnatally Consider Thromboprophylaxis for at least 10 days
If admitted to Hospital consider thromboprophylaxis
If Prolonged admission [≥3 days] or readmission within the puerperium, then consider thromboprophylaxis

Contraindications/Caution to LMWH use
Active antenatal or postpartum bleeding
Women considered at increased risk of major haemorrhage e.g. placenta praevia
Thrombocytopenia [Platelet count <75 × 109/L]
Acute stroke in previous 4 weeks (haemorrhagic or ischaemic)
Severe renal disease [GFR] <30 ml/minute/1.73m2]
Severe liver disease [PT prolonged or known varices]
Uncontrolled hypertension [BP: Systolic BP >200 mmHg or Diastolic BP >120 mmHg]

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